1. Field of the Invention
The present invention relates to a communication system and a communication method, and a gateway.
2. Description of the Related Art
In an Long Term Evolution (LTE) as defined by a Third Generation Partnership Project (3GPP), a Packet data network-Gateway (P-GW) has a function of connecting to an external IP network (hereinafter a Packed Data Network (PDN)), and a protocol for controlling the movement of a mobile terminal uses a GPRS Tunnelling Protocol (GTP). Also, in a mobile IPv4 (MIPv4), a Mobile IPv6 (MIPv6), and a Dual Stack Mobile IPv6 (DSMIPv6) as defined by an Internet Engineering Task Force (IETF), a Home Agent (HA) has a function of connecting to the PDN, and in a Proxy Mobile IPv6 (PMIPv6), a Local Mobility Anchor (LMA) has a function of connecting to the PDN. The HA is used in a communication system as defined by a 3GPP2 and a communication system as defined by a WiMAX forum. Also, the LMA is defined as one of the P-GW functions in the 3GPP. In those specifications, it is basic that an entity having a function of connecting to the PDN assigns the IP address of the mobile terminal.
The operator who operates a plurality of different communication systems may pack a function of connecting to the PDN in one gateway to enable the reduced installation costs and a handover between different communication systems. Also, the operator may manage an address pool separately for each PDN. The address pool is a set of IP addresses assigned to the mobile terminal.
FIG. 1 shows one example of a network configuration view.
This network includes a mobile terminal 101, access networks 102, 103 including a base station or the like, a Foreign Agent (FA) 104 for integrating the access networks and performing the data transfer to an HA 107, a Serving Gateway (S-GW) 105 for integrating the access networks and performing the data transfer to a P-GW 108, and a gateway 106 having the HA 107 and the P-GW 108. The gateway 106 is connected via each PDN #1 to #3 109 to each server #1 to #3 110 in various kinds of protocol.